Thresholds for miles redemption are individual. Everyone in MR is looking for the best mile per dollar value of a flight, but the important figure, IMHO, is the dollar per mile saved by buying tickets in miles instead of dollars.
If I must spend 120,000 miles to buy a ticket worth $6,000, that I would really pay $6,000, then I redeem at 0,050 dollar per mile. It's the true value of my miles. As long as they are not spent, they have no value. If I spend 25,000 miles for a $200 ticket, my value will be 0,008 dollar per mile.
The true value of miles must take into account the "real" value of the award you get. I wouldn't pay $15,000 for a plane ticket. Never. So saying that 200,000 miles can get me a r/t in first JFK-SYD, won't mean that my "mile value" is 0,075 dollar per mile...